Theory
Computed Tomography (CT), which makes use of x-ray tubes (the source) and corresponding detectors oriented in the gantry, forms images by sophisticated computerization. CT can provide high-resolution tomographic images which are helpful in indicating the size and location of a tumor.

Introduction
Our centre have introduced Siemens SOMATOM Definition Flash 256-slice Dual-Source CT Scanner, which is one of the most advanced CT scanners in the market. Compared with previous models, it takes less time,but provides a more precise image and uses low dose of radiation.

The advantages are as follows:

Redefining standards in Cardiology
When performing a cardiac scan, the scan time is only 0.6 s and a full temporal resolution is 75 ms, the new SOMATOM Definition Flash allows scanning the entire heart and evaluating its morphology and coronaries without any beta blockers. Patients suffering from irregular heart rates or atrial fibrillations can be benefit from this high-end cardiac scanner which can perform the scanning that the previous scanner unable to perform.

Reduced Intravenous Contrast Requirement
With rapid volumetric coverage, the duration of vascular contrast opacification required for image acquisition is significantly reduced. This could benefit patients with renal impairment and decrease the risk of contrast-induced nephropathy.

It takes much less time for scanning
Many patients struggle to maintain an adequate breath hold, which results in un-interpretable images and possible need to repeat the scan on older CT scanners, especially children and elderly patients. This scanner only takes 0.6 s for the entire chest scanning at its full speed. Breath-hold can then become optional.

It uses less radiation dose
The 256-slice CT scanner will expose a heart patient to 60 percent less radiation than other older scanners would. Some studies reveal that it can even reduce radiation exposure by 90 percent. One-time exposure to an old 64-slice CT scanner is equivalent to thousands of chest x-rays. Exposure to a 256-slice CT scanner equals to about 100 chest x-rays.

Examination Process
During the scanning process, patient needs to lay on the table and move into the scanner. Radiographer will explain the procedures and ask for patient’s history. They will also instruct the patient how to hold their breath for the examination. If contrast agents need to be used, patient may feel a warm sensation throughout their body. The usual examination time takes about 15-30 minutes.

PreparationsWithout Contrast Injection

1.

No special preparation for head, neck, thorax and extremities regions is required.

Patient may take other regular medications as usual with water only if no endoscopic procedures on the same day.

With Contrast Injection (All regions applied)

1.

Fasting for 4 hours prior to examination.

2.

Patient with Diabetes: DO NOT take oral diabetes medications (i.e. Glucophage, Metformin etc.) 24 hours before and 48 hours after the CT scan.

3.

If patient is over the age of 65 or have Renal Insufficiency and will be receiving IV contrast, he/she must have a Creatinine / RFT drawn within 30 days prior to the exam. Please kindly arrange this lab test for the patient and write down the result on the referral form.

4.

Please notify our staff 48 hours before scheduled appointment if patient is suffering from asthma, kidney diseases, diabetes or any allergies. Oral Steroid (40mg Prednisolone 12 hrs before and 40mg Prednisolone 2 hrs before examination) should be prescribed by referring doctor the day prior for the examination or Hydrocortisone will be injected on the day of examination, extra charge will be applied.

Special note: Upon arrival, patient's heart rate will be monitored before the scan. In order to optimize the images quality and easier to interpret, steadiness is required. If patient's heart rate is unable, medicine will be served orally. This medicine requires at least half to an hour to take effect. Extra charge will be applied. The length of the whole procedure (including all preparations and the actual scan) depends on patient's heart rate. Please expect that patient will be staying at our centre for 1-2 hours.

CT Virtual Colonoscopy

1.

For a successful examination, thorough bowel preparation is needed.

2.

Please send the patient to our centre to collect the bowel-prep kit. Patient may take other regular medications as usual.

3.

If patient is taking iron tablet, please ask patient to stop taking it 4 days before the examination. Patient may take other regular medications as usual.

4.

The day before the examination: Eat a normal breakfast and lunch, but avoid cereals, whole wheat bread or any food containing fibre, seeds or other indigestible materials.

5.

After 2:00pm, and until the examination, patient must not eat anything, only clear fluid is allowed.

6.

At 5:00pm, start to prepare and drink the bowel-prep solution, please contact our centre for details.

7.

Patient should expect watery bowel movement / diarrhea to start within 1-2 hours after taking the bowel-Prep solution. Therefore patient should stay close to a toilet during this period.

Appointment Making
Please make appointment. Please bring relevant old films and reports (e.g. X-rays, CT, MRI etc.) at time of examination for comparison. Please notify our staff if you are pregnant or suspect you are pregnant at the time you make an appointment.